Electromagnetic actuating device



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3 Sheets-Sheet 2 INVENTOR, JAMES c Mam ATTORNEYS United States Patent 3,488,614 ELECTROMAGNETIC ACTUATING DEVICE James C. Macy, North Lavallette, N.J., assignor to Incorporated Thrust, New York, N.Y., a corporation of New York Filed Sept. 20, 1968, Ser. No. 761,263 Int. Cl. H01f 7/08, 3/14 US. Cl. 335-264 14 Claims ABSTRACT OF THE DISCLOSURE An electromagnetic device capable of a strong pull over a long traverse in which a plurality of magnetic discs break up the air gap and electromagnetic coils are loosely placed between the discs.

This invention relates to electromagnetic devices and more particularly to such devices capable of providing a strong pull over a long traverse. This application contains subject matter common to prior applications, Ser. No. 486,454 filed Sept, 10, 1965 (now Patent 3,376,528), Ser. No. 663,792, filed Aug. 28, 1967 and Ser. No. 715,387 filed Mar. 22, 1968, each of these applications being filed in the name of James C. Macy.

Prior electromagnetic actuating devices can generally be classified as either devices providing a relatively short and potentially powerful stroke, or devices providing a relatively weak pull over a long traverse. A conventional electromagnetic relay is typical of the former and a conventional solenoid is typical of the latter.

An object of this invention is to provide an electromagnetic actuating device capable of achieving a strong pull over a long traverse thereby combining the most desirable attributes of prior electromagnetic devices in the two aforementioned categories.

Another object is to provide an electromagnetic actuating device which can provide a strong pull over any desired distance.

Another object is to provide a relatively inexpensive structure capable of achieving a strong pull over a long traverse.

Another object is to provide a multiple coil, multiple magnetic sector actuating device where the separate parts work separately and in concert in a desired manner.

In the actuating device, constructed according to the invention, the working air gap, i.e. the gap to be traversed by the moveable portion of the actuating device, is broken into a number of smaller increments by a number of magnetic segments. When a magnetic flux passes through the magnetic segments, these segments are attracted to one another, or pulled together, to provide the desired movement. By breaking up the working gap in this manner, a long traverse is achieved, but since the individual air gaps are relatively short, a strong pull can, nevertheless, be achieved.

According to a preferred embodiment of the invention, the magnetic flux is produced by means of concentrically wound windings which are disposed perpendicular to the axis of the device and which are loosely accommodated within annular recesses between adjacent magnetic segments. This structural arrangement provides an actuating device much less costly than a comparable unit in which windings are secured to or are part of the magnetic segments. With this structure the magnetic flux paths can be controlled so that the flux generated by a winding first works only to close the working gap associated with the winding and then works to close other gaps.

The foregoing and other objects will become apparent from the following detailed specification which sets forth an illustrative embodiment of the invention. The drawings form part of this specification wherein:

FIGURE 1 is a cross sectional view of an actuating device in accordance with one embodiment of the invention;

FIGURE 2 is an exploded percspective assembly drawing showing details of some of the components for the actuating device shown in FIGURE 1;

FIGURE 3 is a partial cross sectional view illustrating an actuating device according to another embodiment of the invention.

The actuator shown in FIGURES 1 and 2 includes a number of magnetic sectors or discs 10. Each such disc includes an inner hub 11 and an outer ring 12 coupled by a web 13 thereby providing annular recesses extending from opposite flat surfaces of the disc. The flat surfaces of hub 11 near the center of the disc provide a set of inner pole faces 14 and the flat surfaces of outer ring 12 provide a pair of outer pole faces 15. A groove 17 is machined around the outer edge of disc 10 to provide flanges l8 and 19.

An annular winding 20 is located between each adjacent pair of magnetic discs and is accomodated within the annular recesses provided between a pair of adjacent discs when in contact with one another. The wnidings are concentrically wound, preferably about a bobbin, and the leads are brought out through suitable apertures (not shown) in the discs 10. Preferably, the windings are encapsulated in some suitable fashion which provides a relatively smooth exterior surface so that the windings can be loosely positioned within the recesses and move relative to the discs.

End members in the form of end caps 30 and 31 have flat surfaces compatible with the discs, that is, they include recesses 32 and 33, outer flanges 34 and 35 and inner and outer pole faces. Suitable clevis fittings 36 and 37 can be attached as part of the end caps.

A guide rod 40 passes through the center of the actuator unit and through the centers of discs 10. The inside apertures of the discs which accommodate the rod are sufliciently large so that a loose sliding fit is provided thereby permitting the discs to freely move relative to the rod. The ends of rod 40 fit into suitable openings within the end caps. The rod and the co-operating openings are dimensioned so that the rod will not fall out of the openings when the actuator is in a fully expanded position, and so that the rod can be accommodated within the openings when the actuating unit is fully contracted with all of the discs in contact with adjacent discs and end caps.

The separation between adjacent discs is limited by retaining rings 50 which are located surrounding the air gaps between adjacent pairs of discs. The retaining rings are internally flanged and co-operate with the external flanges 18, 19, 34 and 35 of the discs and end caps. Although the retaining rings are shown as closed rings, in practice, it may be more economical to construct these rings of a spring material which is partially open in a C-shaped configuration which can be snapped into place.

The discs and end caps must be made from a magnetic material such as soft iron. Preferably, the rod 40 and the retaining rings 50 are made from a non-magnetic material such as aluminum or brass.

When windings 20 aer energized, -a magnetic flux is created which flows across the air gap between adjacent inner and outer pole faces thereby causing adjacent discs to draw together. As a result, the end caps are pulled toward one another and, since the individual air gaps are relatively short, a strong pull can be achieved over the entire traverse which is equal to the sum of the individual incremental air gaps.

Preferably, the thickness of the webs 13 is controlled so that the magnetic flux of :a particular coil will first work only to close the air gap associated with that coil and will thereafter assist in closing the air gaps associated with other coils. Initially, when a winding is energized the flux will travel around the winding, that is, across the air gap between adjacent outer pole faces, through the web above the winding, across the air gap between adjacent inner pole faces, and through the web below the) winding. The web is sufflciently thick so that there is no magnetic saturation in the web-s when the adjacent discs are fully separated. However, as the air gaps close, the reluctance of the magnetic path decreases and therefore, the flux density in the webs tends to increase. The web thickness is selected so that it becomes saturated just before the associated air gap is closed. As a result the magnetic flux must seek a new path which would be across other air gaps thereby helping to close the other gaps. Ultimately, when all of the gaps are closed, a portion of the flux from each of the coils will flow through the end caps and hence, it is necessary that the end caps be sufficiently thick to avoid saturation under these cir cumstances.

FIGURE 3 illustrates another embodiment which is similar to FIGURES 1 and 2, except that the windings 20 are loosely accommodated in recesses which extend only from one side of the associated discs. Accordingly, the webs '13 of the discs form part of the flat outer surface instead of being at the center of the disc. In some circumstances, this embodiment may be preferable since it is somewhat easier to construct. In operation, however, it is basically the same as the unit illustrated in FIGURES 1 and 2.

Although only a few illustrative embodiments have been described in detail it should be obvious that there are numerous variations contemplated within the scope of the invention. For example, the individual coils could be electrically connected for independent energization to provide a controlled sequential closure. The working gaps between the discs could be filled with a magnetic fluid to replace the air in the gap, this technique being more fully described in the aforementioned copending application Ser. No. 715,387. The path of movement could be other than linear as, for example, the discs could be shaped to permit a movement along a circular axis. The scope of the invention is more particularly defined in the appended claims.

What is claimed is:

1. In a magnetic actuating device, the combination of:

a plurality of magnetic members adapted for relative movement along a predetermined path;

a plurality of concentrically wound electromagnetic windings disposed perpendicular to said path;

an annular recess for loosely accommodating an electromagnetic winding between each adjacent pair of said magnetic members when in contact with one another; and

means for limiting the separation between adjacent magnetic members.

2. An actuating device according to claim 1 wherein said relative movement is linear and said predetermined path is an axis for said magnetic members and said electromagnetic windings.

3. An actuating device according to claim 2 further including a guide rod disposed along said axis.

4. An actuating device according to claim 1 wherein said magnetic members are of a generally disc configuration.

5. An actuating device according to claim 4 wherein said magnetic members are externally flanged and wherein said means for limiting separation is in the form of rings with cooperating internal flanges.

6. In a magnetic actuating device, the combination of:

a pair of relatively moveable end members forming a wo i a the ebe e ag a plurality of magnetic disc members disposed to breakup said working gap into smaller increments; a plurality of electromagnetic windings located between adjacent one of said magnetic disc members;

annular recesses in said magnetic disc members for loosely accommodating one of said windings between each adjacent pair of disc members; and

means for limiting the separation between adjacent magnetic disc members.

7. Actuating device according to claim 6 further including a guide rod passing through the center of said disc members and said electromagnetic windings, said guide rod being accommodated within co-operating openings in said end members.

8. An actuating device according to claim 6 wherein each of said magnetic disc members includes only one annular recess therein.

9. An actuating device according to claim 6 wherein each of said magnetic disc members includes a pair of similar annular recesses extending from opposite surfaces of the disc.

10. In a magnetic actuating device, the combination of:

a pair of relatively moveable end members forming a 1 working gap therebetween;

a plurality of magnetic members disposed to break up said working gap into smaller increments, each of said magnetic members including:

inner and outer pole faces adjacent incremental working gaps between adjacent magnetic members;

magnetic means coupling said inner pole faces to said outer pole faces; and

a. recess between said inner and said outer pole faces;

a plurality of electromagnetic windings accommodated in said recesses;

said magnetic means coupling said inner pole faces to said outer pole faces having a cross-section which becomes magnetically saturated upon closure of the associated incremental working gap; and

means for limiting the separation between adjacent magnetic members.

11. A magnetic actuating device according to claim 10 wherein said magnetic members have a generally disc configuration with an inner hub and outer ring forming said pole faces and a web therebetween, said recesses being located between said hubs and rings.

A magnetic actuating device according to claim 11 wherein said web is centrally located in said discs and said recesses extend from opposite flat surfaces of the disc.

A magnetic actuating device according to claim 11 wherein said recesses extend from one surface of said discs and said webs are located along the opposite surface.

14. A magnetic actuating device according to claim 11 wherein the thickness of the web of each disc is controlled to create said magnetic saturation upon closure of the associated working gap.

References Cited UNITED STATES PATENTS 548,601 10/1895 Black 335-259 XR 1,699,866 1/1929 Werner 335264 2,881,367 4/1959 Watson 335279 XR 2,935,663 5/1960 Pollack 335264 XR G. HARRIS, Primary Examiner US. Cl. X.R 335267, 296 

